[Profiler] Fix HTML plot output for profiler export_memory_timeline (#101316)
Summary: Wrap the PNG image of the memory plot inside of an HTML body, so that the file can be easily opened or embedding in other frontends.
Test Plan:
CI Tests
# Ran locally on Resnet50:
{F988498243}
{F988498789}
https://www.internalfb.com/manifold/explorer/trace_stats/tree/749163530321413/tmpj3ifzs7r.pt.memorytl.html
Differential Revision: D45827509
Pulled By: aaronenyeshi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101316
Approved by: https://github.com/xuzhao9
